Phenanthroline ligands with divergent pyridine units

Article abstract of DOI:10.3184/030823409X401817

2-Mono- and 2,9-di-substituted 1,10-phenanthrolines with 4-pyridine units attached either via 1,4-phenylene- or 4-ethynyl-phenyl spacers, have been synthesised. The strategy is based on the introduction of 4-trimethylsilylphenyl group(s) at the phenanthro

Full text of DOI:10.3184/030823409X401817

JOURNAL OF CHEMICAL RESEARCH 2009
MARCH, 133-136
RESEARCH PAPER 133
Phenanthroline ligands with divergent pyridine units
Myroslav O. Vysotsky*
Abteilung fur Lehramtskandidaten
der Chemie, Fachbereich Chemie, Pharmazie und Geowissenschaften,
Johannes Gutenberg-
Universitiit, Mainz 55128, Germany
2-Mono- and 2,9-di-substituted
1,10-phenanthrolines
with 4-pyridine units attached either via 1,4-phenylene- or
4-ethynyl-phenyl spacers, have been synthesised. The strategy is based on the introduction of 4-trimethylsilylphenyl
group(s) at the phenanthroline core with the subsequent ipso-substitution ofTMS groups by bromine or iodine and
successive Suzuki or Sonogashira reactions with 4-pyridineboronic acid or 4-ethynylpyridine, respectively.
Keywords: phenanthroline, pyridine, TMS-protection, Sonogashira, Suzuki
I,IO-Phenanthrolines are known first for their ability to form
stable complexes with transition metal cations.1,2 Depending
on the nature of metal, such complexes demonstrate rich
photochemical properties,3 that are successfully used in
analytical and various biochemical applications.4,5 Homo-
and hetero-Ieptic complexes of 2,9-disubstituted derivatives
of this heterocycle with copper(I) in the ratio 2: I, have
been efficiently used in templated syntheses of such
mechanically interlocked molecules as rotaxanes,6 catenanes,7
doubly braded [2]-catenanes8 and knots.9 Introduction of
additional complexation units (e.g. bi-pyridines) enabled the
possibility of the use of these building blocks in assemblies
of large structures on the nanometre scale.1°-12The use of
2,9-disubstituted I,IO-phenanthrolines has inspired the
formulation of the appealing concept of concave reagents.13
Obviously, realisation of different goals including the
self-assembled structures needs different derivatives of
I, 10-phenanthroline. In this article are described convenient
syntheses of various ligands containing one or two
4-pyridyl units rigidly coupled to the positions 2,9- of the
1,IO-phenanthroline core either via 1,4-phenylene or via
4-ethynyl-phenyl (-C6Hc C"'C-) spacers, which have not
been described previously to the best of my knowledge. Such
molecules might be used in self-assembly of new structures
on the nanometre scale.14 The analogous compounds with
pyridine units attached via longer spacers have been already
described. The difference in the length is one diphenyloxide
unit, which also possesses a kink. The self-assembly of these
compounds via copper (I) and palladium (II) cations leads to
the formation of [2]-catenanes.15
The strategy proposed is based on the introduction of one or
two 4-trimethylsilyl-phenyl group(s) at the positions 2- and 9-
of the phenanthroline core, subsequent ipso-substitution of the
TMS-groups by halogens (bromine or iodine) and successive
C-C coupling using either Suzuki 16or Sonogashira 17reactions.
The synthesis of the phenanthroline derivatives having
either one or two 4-bromo-phenyl groups, has been already
described.15 The preparation of these compounds proposed in
here, is simply the alternative to the already method described
and allows the formation of much more soluble trimethylsilyl
intermediates. On the other hand, the latter can be used for
synthesis of even more reactive iodo- derivatives (see later)
and potentially for the introduction of other electrophiles via
the analogous ipso-substitution of the TMS groups.18
Addition of halogen to a pre-cooled solution of the TMS
derivatives(s) in dichloromethane, leads to the nearly
immediate formation of a precipitate in all cases. However,
using stoichiometric amounts of halogenating agents did not
lead to complete reactions. This was proved by the presence
of the residual signal at Ii 0.37 ppm of the Ar-Si(CIL)3 group
(in DMSO-D6) and a double set of some signals in the
aromatic region of the 1H NMR spectrum of a crude product
(after evaporation of the solvent).
An elemental analysis of the precipitate formed during
the bromination reaction of 2 with 3.3 mole-equivalents of
bromine (found: C 36.93, H 2.01, N 4.75) is much different
from the expected one for 5 (calculated: C 58.81, H 2.88,
N 5.71). This sample had been dried carefully under high
vacuum for 24 h without heating before it was submitted to
elemental analysis and a mixture ofthe complexed bromonium
salts with two different counter-anions (for the complex
(5'Br+)Br calculated: C 44.35, H 2.17, N 4.31; and (5'Br+)Brf
calculated: C 35.60, H 1.74, N 3.46) is suggested with the
prevalence of the latter, rather than either the presence of traces
of the solvent (for 5'(CH2CI2) calculated: C 52.21, H 2.80, N
4.89) or salt (for (5'W)Br calculated: C 50.47, H 2.65, N 4.90).
Such complexation obviously reduces the reactivity I) of the
aromatic system itself; 2) of a halogenating agent (Hal+) due to
the surprisingly strong complexation occurring. This explains
the need for one additional mole-equivalent of the halogen
to complete the reaction. To destroy an excess of halogen,
bromotrimethylsilane and complexes of phenanthroline
with Hal+ at the end of the reaction, the solvent is removed
under reduced pressure and the crude product is solubilised
under a short reflux in a mixture of ethyl acetate, methanol
and triethylamine. The crude product is then pre-adsorbed
on silica and purified using column chromatography. The
yields of these reactions are within 70-91 %, which is quite
acceptable.
After a period of trial and error it became clear that bromo
derivatives are better suited for Suzuki reaction than iodo
ones in the conditions used, since in the former case the lower
amounts of by-products are formed (due to the lowerreactivity).
The reaction of mono bromo derivative
3 (Scheme 2),
has been carried out in a mixture of 1,2-dimethoxyethane and
water, giving the desired product 7 in 77% yield. The small
amount of by-products formed in this reaction and the not
too complicated purification makes this reaction easy even in
unexperienced hands. However, the solvent mixture used here
is not suited for reaction with the dibromo derivative 5 due to
solubility problems. Unfortunately, the formation of a mixture
of at least four compounds due to the side reactions is observed.
4,4'-Bipyridyl (due to the homo-coupling of 4-pyridineboronic
acid) was identified among the products of this reactions.
In all cases, the purification is very inconvenient and never led
to an analytically pure product. Although changing the solvent
mixture to DMSO containing 10% water, increases the yields
of 8 up to 86% after column chromatography (assuming
The typical addition oflithium-para-trimethylsilyl-benzene
(readily obtained from l-bromo-4-trimethylsilylbenzeneI9)
to
the phenanthroline with successive rearomatisation2o leads to
the formation of the expected compound 1 with the yields of
75-80% (Scheme I). The introduction of the second 4-TMS-
phenyl group also goes smoothly with the lower but still
acceptable yield of 63%.
* Correspondent.E-mail:m.vysotsky@yahoo.de

134 JOURNAL OF CHEMICAL RESEARCH 2009
~'<:
~ N
Li
I
,
N
2) Mn02
I~
Br20rj
Br20r j
ICI
ICI
x
X
X
X
=
=
Br
I
X
= Br
3
4
5
6
X=I
Scheme
1
8
Hb
8
Hb
N
N
)0
)0
3
5
tert.-BuOK,
tert.-BuOK,
Pd(PPh3).
Pd(PPh3).
7
N
H
H
~'
~I
~
~I
~
N
N
)0
)0
4
6
Pd(PPh3).
Pd(PPh3).
EtN(i-Pr),
EtN(i-Pr),
7
7
,
I
~
N
~
N
Scheme 2
only the formation of this product), its purity remains no
higher than 85% on the basis of IH NMR spectra. Neither
crystallisation of this product nor flash chromatography led to
the higher purity.
On the other hand, the Sonogashira reaction (Scheme 2)
always gives reproducible and very satisfactory results. This
reaction has always been carried out in the absence of copper(I)
halides, since in this case one avoids the destruction of the
copper complexes with phenanthrolines or their removal from
the crude product.21 Di-iso-propylamine is used as a base.
All in all, the crude products after this reaction are much easier to
purifYthan the ones after Suzuki reaction with 5. The yields are
moderate (60-66%), but there are no experimental difficulties
in the synthesis of 9 and 10. As in the case of 7, this pair of
compounds can be also synthesised in less experienced hands.
In conclusion, the syntheses of phenanthroline derivatives
containing one or two pyridine units attached to the 1,10-
phenanthroline core at the second and ninth positions via
1,4-phenylene or 4-ethynyl-phenyl spacers, are described.
The trimethylsilyl protection strategy has been chosen to
prepare 4-bromo- and 4-iodo-phenyl precursors, which have
been then converted into the desired products either via Suzuki
or Sonogashira reactions. The compounds of this type might
be interesting for the self-assembly oflarge structures.

JOURNAL OF CHEMICAL RESEARCH 2009 135
2-(4-Iodophenyl)-1,lO-phenanthroline
(4): A 1M solution of
Experimental
iodochlorine (2.50 mL, 2.50 mmol) was added in one portion to a
solution of 1 (0.275 g, 0.837 mmol) in dichloromethane (20 mL).
A white precipitate was formed nearly immediately. The reaction
mixture was stirred for 1.5 days. The reaction mixture was evaporated
All chemicals have been purchased from Acros and Aldrich if not
stated otherwise, and used without further purification. All solvents
used, were of p.a. grade (99.5+%) while the ones used for purifications
(>99%) were additionally distilled. Melting points were determined
with a MEL TEMP 2 capillary melting point apparatus and are not
corrected. 'H and l3C NMR spectra were measured on a Broker
Avance DRX400 spectrometer at 25°C at 400 MHz and 100 MHz
working frequencies, respectively. The chemical shifts are given
in respect to the positions of the residual solvent signals. FD and
ESI mass spectra were measured on a Finnigan MAT 8230 and
Micromass QTOF Ultima 3 instruments. l-bromo-4-trimethylsilyl-
benzene was readily obtained from 1,4-dibromobenzene in 90-95%
yields.19 All reactions were carried out under an inert atmosphere if
not stated otherwise. The work with all compounds (especially with
the new ones) requires the maintenance of all necessary safety rules.
under reduced pressure to dryness.
A mixture of ethyl acetate
(40 mL), methanol (20 mL) and triethylamine (6 mL) was added
and the residue was dissolved on gentle heating. The mixture was
evaporated under reduced pressure. THF (30 mL) was added and the
solution was filtered from the precipitate (triethylammonium chloride
and iodide) then pre-adsorption on silica (I g) was carried out.
The column chromatography on silica using a mixture of ethyl acetate
and petroleum ether (2: I v/v) yielded 240 mg (75%) of 4 (yellowish
crystals). M.p. 172-173°C. 'H NMR (DMSO-D6) 8: 7.80 (dd,
J, = 8.2 Hz, J2 = 4.0 Hz, 1H), 7.98 (d, J = 8.2 Hz, 2H), 7.99 and 8.03
(two d of AB system, J = 8.8 Hz, 2H), 8.25 (d, J = 8.2 Hz, 2H), 8.40
(d, J = 8.5 Hz, 1H), 8.51 (dd, J, = 8.2 Hz, J2 = 1.2 Hz, 1H), 8.59 (d,
J= 8.5 Hz, 1H), 9.17 (dd, J, = 4.1 Hz, J2 = 1.5 Hz, 1H). 'H NMR
(CDCI3) 8: 7.70 (dd, J, = 8.2 Hz, J2 = 4.1 Hz, 1H), 7.84 and 7.87
(two d of AB system, J = 8.8 Hz, 2H), 7.93 (d, J = 8.2 Hz, 2H), 8.12
(d, J= 8.5 Hz, 1H), 8.14 (d, J= 8.5 Hz, 2H), 8.32 (dd, J, = 8.2 Hz,
J2 = 1.2 Hz, 1H), 8.36 (d, J = 8.4 Hz, 1H), 9.29 (dd, J, = 4.4 Hz, J2 =
1.7 Hz, 1H). l3C NMR (CDCI3) 8: 96.0, 120.2, 123.0, 126.4, 126.5,
127.7, 129.1, 129.6, 136.3, 137.0, 137.9, 138.9, 145.9, 146.0, 150.3,
156.3. MS (FD): m/z Calcd for C'8HllN2I M+: 382.2. Found: 382.0.
Anal. Calcd for C'8HllN2I: C, 56.57; H, 2.90; N, 7.33. Found: C,
56.74; H, 2.89; N, 7.33%.
2-(4- Trimethylsilylphenyl)-l, lO-phenanthroline (1):
A solution
of l-bromo-4-trimethylsilyl-benzene (6.67 g, 29.1 mmol) in THF
(130 mL) was cooled to ~ -85°C (acetone-dry ice bath, additionally
cooled via the addition of liquid nitrogen) with stirring and
2.5 M solution of n-butyllithium in hexane (11.8 mL, 29.40 mmol)
was added dropwise. The reaction mixture was stirred at -85 to
80°C for 30 minutes and then the cooling bath was removed and
phenanthroline (3.93 g, 21.8 mmol) was added in one portion.
The reaction mixture was stirred on an ice bath during 6 h (the
temperature should not be higher than 100c) and then a concentrated
solution of ammonium chloride (60 mL) was added. The organic
layer was separated and the aqueous layer was extracted with ether
(4 x 40 mL). The combined organic layers were dried over magnesium
sulfate, filtered and evaporated under reduced pressure. The residue
was dissolved in dicWoromethane (30 mL) and magnesium (IV) oxide
(22.76 g, 0.267 mol) was added in one portion. The reaction mixture
was stirred overnight in an open flask and then filtered through
a short plug of silica and evaporated. The oily residue was treated
with hot petroleum ether, which was allowed to cool slowly to room
temperature and decanted. The residue was washed with petroleum
ether (3 x 20 mL) and dried yielding 5.94 g (83%) of the desired
product as a yellow viscous oil. 'H NMR (CDCI3) 8: 0.32 (s, 9H),
7.62 (dd, J, = 8.0 Hz, J2 = 4.4 Hz, 1H), 7.68 (d, J = 8.1 Hz, 2H), 7.75
and 7.80 (two d of AB system, J = 8.8 Hz, 2H), 8.09 (d, J = 8.4 Hz,
1H), 8.23 (dd, J, = 8.1 Hz, J2 = 1.8 Hz, 1H), 8.27 (d, J = 8.2 Hz, 1H),
8.29 (d, J = 8.1 Hz, 2H), 9.22 (dd, J, = 4.1 Hz, J2 = 1.7 Hz, 1H).
l3CNMR (CDCI3) 8: -1.16, 120.6, 122.8, 126.2, 126.3, 127.1, 127.5,
129.0, 133.7, 136.0, 136.7, 139.9, 141.8, 146.1, 146.4, 150.4, 157.6.
MS (FD): m/z Calcd for C2,H2oN2Si M+: 328.5. Found 328.3. Calcd
for C2,H20N2S·0.5HP: C, 74.75; H, 6.27; N, 8.30. Found: C, 75.16;
H, 6.31; N, 8.27%.
2,9-Bis(4-bromophenyl)-1,lO-phenanthroline
(5): The compound
was obtained analogously to 3 using the same ratio of bromine to
2, with the yield of 83% (yellowish crystals). M.p. 222-223°C
(lit.'s 219-221 0c). 'H NMR (DMSO-D6) 8: 7.83 (d, J = 8.5 Hz,
4H), 8.02 (s, 2H), 8.43 (d, J = 8.4 Hz, 2H), 8.48 (d, J = 8.5 Hz, 4H),
8.60 (d, J= 8.4 Hz, 2H). l3C NMR (CDCI3) 8: 119.8,124.1,126.2,
128.1, 129.1, 132.0, 137.1, 138.2, 146.9, 155.7.
2,9-Bis(4-iodophenyl)-1,lO-phenanthroline
(6): The compound
was obtained analogously to 4 using 3.6 equivalents of iodocWorine.
The crude product was purified on silica column using a mixture
of ethyl acetate and petroleum ether (I: I v/v) giving a yellowish
crystalline compound with the yield of 91%. M.p. 233-235°C (with
decomp.). 'H NMR (DMSO-D6) 8: 8.00 (d, J = 9.1 Hz, 4H), 8.01
(s, 2H), 8.30 (d, J= 8.2 Hz, 4H), 8.41 (d, J= 8.2 Hz, 2H), 8.60 (d,
J= 8.2 Hz, 2H). l3C NMR (DMSO-D6) 8: 96.9, 119.9, 126.3, 128.0,
129.3, 137.7, 138.0, 144.7, 154.3. MS (FD): m/z Calcd for C24H'4N2I2
M+: 584.2. Found: 584.3. Anal. Calcd for C24H'4N2I2: C, 49.34, H,
2.42; N, 4.80. Found: C, 49.42; H, 2.42; N, 4.80%.
2-(4 '-(4 "-Pyridyl)phenyl)-l, 1O-phenanthroline (7):
A
solution
of potassium tert-butoxide (0.728 g, 6.50 mmol) in water (3 mL)
was added in one portion to a solution of 3 (0.234 g, 0.698 mmol)
and tetrakis(triphenylphosphine) palladium(O) (81 mg, 69.8 flmol)
in 1,2-dimethoxyethane (8 mL) and the mixture was purged with
nitrogen for 10 min. The reaction mixture was stirred at 84°C for
12h under a nitrogen atmosphere. Then water (50 mL) was added. The
precipitate was filtered off, washed with water (3 x 10 mL) and dried.
The residue was pre-adsorbed on silica (6 g) and eluted using mixture
oftetrahydrofuran and methanol (I: lv/v). 180 mg (77% yield) of the
desired product were obtained. M.p. 221-223 °C. 'H NMR (DMSO-
D6) 8: 7.80 (dd, J, = 8.2 Hz, J2 =4.4Hz, 1H), 7.81 (d, J= 6.2 Hz, 2H),
7.99 and 8.02 (two d ofAB system,J= 8.8 Hz, 2H), 8.04 (d,J= 8.2 Hz,
2H), 8.45 (d, J = 8.5 Hz, 1H), 8.50 (dd, J, = 8.2 Hz, J2 = 1.5 Hz,
1H), 8.59 (d, J= 8.2 Hz, 3H), 8.68 (d, J= 6.2 Hz, 2H), 9.19 (dd,
J, = 4.1 Hz, J2 = 1.8 Hz, 1H). l3C NMR (DMSO-D6) 8: 120.4,
121.4, 123.7, 126.7, 127.0, 127.5, 128.0, 128.3, 129.2, 136.6, 137.7,
138.2, 139.8, 145.6, 145.9, 146.6, 150.3, 150.6, 155.0. HRMS (ESI):
m/z Calcd for C23H'6N3 [M + H]+: 334.1341, Calcd for C23H,sN3Na
[M + Na]+: 356.1161, Found: 334.1363 (14%), 356.1176 (100%).
Anal. Calcd for C23H'6N3·0.25HP: C, 81.75; H, 4.62; N, 12.43.
Found: C, 81.98; H, 4.72; N, 12.23%.
2, 9-Bis(4-trimethylsilylphenyl)-1,1 O-phenanthroline
(2):
This
compound was obtained analogously to 1. After the oxidation step
with manganese (IV) oxide, the crude product was purified on a
silica column using ethyl acetate: petroleum ether (I : I v/v) mixture
as an eluant giving the desired compound in 63% yield (yellowish
crystals). M.p. 282°C. 'H NMR (CDCI3) 8: 0.35 (s, 18H), 7.75
(d, J= 7.9 Hz, 4H), 7.77 (s, 2H), 8.14 (d, J= 8.2 Hz, 2H), 8.29 (d,
J = 8.2 Hz, 2H), 8.44 (d, J = 7.9 Hz, 4H). l3CNMR (CDCI3) 8: -1.07,
120.0, 126.0, 126.8, 128.0, 133.9, 136.8, 139.8, 141.9, 146.2, 156.9.
MS (FD): m/z Calcd for C30H32N2Si2M+: 476.7. Found: 476.4. Anal.
Calcd for C30H32N2Si2:C, 75.57; H, 6.77; N, 5.87. Found: C, 75.56;
H, 6.87; N, 5.86%.
2-(4-Bromophenyl)-1,lO-phenanthroline
(3): A solution of 1
(0.184 g, 0.56 mmol) in dichloromethane (12 mL) was first pre-cooled
to ~ 10°c on an ice/water bath and bromine (0.296 g, 1.85 mmol)
was added in one portion. The cooling bath was removed and
the reaction mixture was stirred at room temperature for
6 h.
During this period of time a yellow precipitate was formed. The
reaction mixture was evaporated and dried under reduced pressure.
The residue was dissolved in a mixture of ethyl acetate (30 mL),
methanol (I 5mL) and triethylamine (3 mL). Thesilica(~3 g)was added
and the mixture was evaporated gently under reduced pressure and
dried. The column chromatography (ethyl acetate and petroleum ether
(2: I v/v)) gave 0.131 g (70%) of3 (white crystals). M.p. 179-180°C
(lit.'s 187-189°C). 'H NMR (DMSO-D6) 8: 7.80 (dd, Js can not be
found due to the overlap with the next signal, IH), 7.81 (d, J= 8.5 Hz,
2H), 8.00 and 8.03 (two d of AB system, J= 8.8 Hz, 2H), 8.42 (d,
J = 8.5 Hz, 3H), 8.52 (dd, J, = 8.2 Hz, J2 = 1.4 Hz, 1H), 8.60 (d,
J= 8.5 Hz, 1H), 9.17 (dd, J, = 4.1 Hz, J2 = 1.5 Hz, 1H). l3C NMR
(DMSO-D6) 8: 120.2, 123.0, 123.9, 126.3, 126.5, 127.7, 129.1, 129.5,
131.9,136.2,137.0,138.4,146.1,146.3,150.4,156.2.
2,9-Bis(4'-(4"-pyridyl)phenyl)-1,lO-phenanthroline
(8): A mixture
of
5
(85 mg, 0.173 mmol), 4-pyridineboronic acid (64 mg,
0.520 mmol) and potassium hydroxide (57 mg, 0.867 mmol) in a
mixture of dimethylsulfoxide (12 mL) and water (1.2 mL) had been
first heated gently until all reagents were dissolved. The mixture
was cooled to room temperature, purged with nitrogen and tetrakis
(triphenylphosphine)palladium(O) (20 mg, 17.3 flmol) was added
and the reaction mixture was stirred at 45°C for 2 h under a nitrogen
atmosphere. Then water (50 mL) was added and the precipitate
formed was filtered off and dried. Then the residue was dissolved
in a mixture ofTHF and methanol (1:1, v/v), silica (5 g) was added
and the solvent was carefully evaporated under reduced pressure.

136 JOURNAL OF CHEMICAL RESEARCH 2009
After the solid was dried, column chromatography on silica using
first a mixture ofTHF: petroleum ether (2: I, v/v) and then THF, gave
72 mg (86%) of 8 (~85% purity, that could not be improved under the
conditions applied). M.p. >245 °C (decomposition). 'HNMR (DMSO-
J
=
6.0 Hz, 4H), 7.77 (d, J
J= 6.0 Hz, 2H), 8.33 (d, J= 8.4 Hz, 2H), 8.49 (d, J= 8.3 Hz, 4H),
8.63 (d,J= 6.0 Hz, 4H). 'HNMR(DMSO-D6) 8: 7.59 (d,J= 5.8 Hz,
= 8.3 Hz, 4H), 7.81 (s, 2H), 8.16 (d,
4H), 7.89 (d, J= 8.5 Hz, 4H), 8.06 (s, 2H), 8.50 (d, J= 8.5 Hz, 2H),
8.60-8.70 (m, 10H). 'H NMR (THF-D8) 8: 7.43 (d, J= 5.8 Hz, 4H),
7.78 (d, J= 8.2 Hz, 4H), 7.89 (s, 2H), 8.33 (d, J= 8.4 Hz, 2H), 8.43
(d, J= 8.4 Hz, 2H), 8.59 (d, J= 5.8 Hz, 4H), 8.66 (d, J= 8.2 Hz, 4H).
l3C NMR (CDCI3) 8 : 88.1,94.0, 120.1, 123.1, 125.6, 126.4, 127.6,
128.2, 131.5, 132.4, 137.1, 140.0, 146.1, 149.8, 155.7. HRMS (ESI):
m/z Calcd for C38H23N4[M + H]+: 535.1918. Found: 535.1921. Anal.
Calcd for C38H22N4·0.5HP: C, 83.96; H, 4.17; N, 10.30. Found: C,
83.53; H, 4.56; N, 9.18%.
D6) 8: 7.87 (d, J = 5.8 Hz, 4H), 8.05 (s, 2H), 8.11 (d, J = 8.3 Hz,
4H), 8.53 and 8.64 (two d of AB system, J= 8.4 Hz, 4H), 8.71 (d,
J= 5.8 Hz, 4H), 8.72 (d, J= 8.3 Hz, 4H). 'H NMR (THF-D8) 8: 7.72
(d, J= 4.6 Hz, 4H), 7.88 (s, 2H), 7.99 (d, J= 7.4 Hz, 4H), 8.36 (d,
J= 8.4 Hz, 2H), 8.44 (d, J= 8.4 Hz, 2H), 8.66 (d, J= 4.6 Hz, 4H),
8.75 (d, J
= 7.4 Hz, 4H). l3C NMR (DMSO-D6) 8: 120.1, 121.1,
126.3, 127.3, 127.9, 128.0, 137.5, 137.9, 139.5, 145.3, 146.3, 150.2,
154.5. l3C NMR (THF-D8) 8: 120.4, 121.9, 127.0, 128.0, 129.0,
129.2, 137.6, 139.8, 141.2, 147.4, 148.0, 151.3, 156.1. HRMS (ESI):
m/z Calcd for C34H23N4[M + H]+: 487.1918, Calcd for C34H22N4Na
[M +Na]+: 509.1738. Found: 487.1945 (10%), 509.1741 (100%).
I thank Volker Bohmer (Mainz) for illuminating discussions
and generous support. This work was financially supported
by the Deutsche
2-(4'-(4 "-Pyridyl-ethynyl)phenyl)-l, 1O-phenanthroline
(9):
Forschungsgemeinschaft
(Forschungs-
A mixture of mono iodo derivative 4 (266 mg, 0.696 mmol), 4-
ethynylpyridine (106 mg, 1.03 mmol) [the commercially available
hydrochloride can be used instead] in DMF (2 mL) and di-iso-
propylamine (I mL) was purged with nitrogen for 10min, then tetrakis
(triphenylphosphine)palladium(O) (82.4 mg, 70.0 flmol) was added
and the reaction mixture was stirred at 60°C (temperature of the oil
bath) for 3 h and then cooled to the room temperature. Water (20 mL)
was added and the precipitate formed was filtered off, pre-adsorbed on
silica and purified on a silica column (THF: petroleum ether 3 :2 v/v
mixture to wash first by-products, then pure THF), that gave 150 mg
(60%) of the desired product. M.p. 241-243°C. 'H NMR (DMSO-
stipendium
06.2008, Vy6/1).
in 2004-2005, then "Eigene Stelle" 07.2006-
Received 18 September 2008; accepted 13 December 2008
Paper 08/0180 doi: 10.3184/030823409X401817
Published online: 6 April 2009
References
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D
6) 8: 7.59 (d, J
=
6.0 Hz, 2H), 7.82 (dd, J,
8.4 Hz, 2H), 8.01 and 8.05 (two d of AB system,
8.8 Hz, 2H), 8.48 (d, J 8.5 Hz, 1H), 8.52 (dd, J, 8.1 Hz,
1.7 Hz, 1H), 8.57 (d, J= 8.4 Hz, 2H), 8.62 (d, J= 8.5 Hz, 1H),
6.0 Hz, 2H), 9.19 (dd, J, 4.3 Hz, J2 1.7 Hz, 1H).
'H NMR (CDCI3) 8: 7.41 (d, J = 6.0 Hz, 2H), 7.64 (dd, J, = 8.0 Hz,
J2 4.4 Hz, 1H), 7.72 (d, J 8.2 Hz, 2H), 7.78 and 7.81 (two d
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1H), 7.86 (d, J
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=
6
8.66 (d, J
=
=
=
7
8
=
=
of AB system, J= 8.8 Hz, 2H), 8.11 (d, J= 8.4 Hz, 1H), 8.25 (dd,
J, =8.0Hz,J2= 1.7Hz, 1H), 8.32 (d,J= 8.4 Hz, 2H), 8.61 (d,J= 8.5 Hz,
9
1H), 9.24 (dd, J, = 4.4 Hz, J2
88.0, 94.0, 120.5, 122.9, 123.0, 125.5, 126.3, 126.7, 127.8, 127.9,
129.1,131.4,132.3,136.1,137.0,140.1,146.2, 146.4, 149.8, 150.5,
= 1.4 Hz, 1H). l3C NMR (CDCI3) 8:
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156.2. MS (FD): m/z Calcd for C2sH,sN3 M+: 357.4. Found: 357.2.
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83.97; H, 4.28; N, 11.68%.
2, 9-Bis(4 '-(4"-pyridyl-ethynyl)phenyl)-l ,1O-phenanthroline (10).
A mixture of 6 (159 mg, 0.272 mmol), 4-ethynylpyridine (70.2 mg,
0.68 mmol) [the commercially available hydrocWoride can be used
instead] in DMF (2 mL) and di-iso-propylamine (4 mL), was purged
with nitrogen during 10 minutes, then tetrakis( triphenylphosphine)
palladium(O) (31.5 mg, 27.2 flmol) was added and the reaction
mixture was stirred at 60°C (temp. of the oil bath) for 3 h and then
cooled to the room temperature. Diethyl ether (25 mL) was added and
the precipitate formed was filtered off, washed with ether (3 x 3 mL),
dried and washed with water. After drying, 100 mg (66%) of10 were
obtained. M.p. >220°C (decomp.). 'H NMR (CDCI3) 8: 7.42 (d,
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